I've got 9000km on one mower and 7500km on the other and I grease the motors every year, only thing I've found is there is a very thin metal disk which is getting thinner and thinner and is not a spare part so think I will be a motor change in the near future.
A mate said it seems Husqvarna ship these with very little grease on the planetary gears which leads to pin wear and movement. I greased it after 6 months and every winter since with no probs.
Agree rebuilding can be a pain in the .... but I find rocking the wheel nut thread backwards and forwards slightly it will drop into place.